Refers to a school or university club focused on mountaineering and hiking.
He joined the mountaineering club in high school.
mountain area; mountainous region
A somewhat formal or literary term for a mountainous area; in everyday speech, 山間部 or 山地 is more common.
Rare plants can be found in that mountainous area.
Compound of 山岳 (mountain) + 部 (club, section, or area). The derivation is straightforward from the kanji meanings.